Pressure swirl atomizers are used in various applications, including fuel injection systems and exhaust aftertreatment systems. Atomizers disperse fluid into a fine spray by directing fluid from tangential swirl channels into a swirl chamber and then opening a central exit orifice to allow the fluid to exit in a spray pattern. More particularly, the tangential swirl channels causes fluid entering the swirl chamber to swirl in a circular motion and increase its angular velocity as it moves toward the exit orifice. The centrifugal force generated by the swirling motion generates a low pressure zone along the central axis of the swirl chamber.
When the exit orifice is opened, exhaust gas enters the atomizer through the exit orifice and forms an air core through the exit orifice. The fluid forms a “wall” around the air core. Aerodynamic forces break the fluid wall into droplets after it exits the injector. The thickness of this fluid wall and the dimensions of the air core depend on the fluid supply pressure and on the ratio of the diameter of the swirl chamber and the diameter of the exit orifice, and these dimensions in turn control the characteristics of the spray pattern as fluid leaves the exit orifice.
A solenoid-controlled pintle opens and closes the exit orifice to allow or block fluid flow out of the atomizer. In applications where a variable flow rate is desired, the exit orifice may be opened and closed via pulse width modulation (PWM) of the pintle between the open and closed positions. When the solenoid is energized, it generates a magnetic force that pulls the pintle away from the exit orifice and toward a pole piece until the pintle seats against the pole piece. When the solenoid is de-energized, the pintle should return to the closed position and block the exit orifice. However, the pintle may stick in the open position, creating an unpredictable response delay before the exit orifice is closed again. This delay makes it difficult to obtain consistent fuel flow, especially at high duty cycles.
There is a desire for a pressure swirl atomizer having a more predictable, consistent pintle response.